I changed out the switch on the light fixture in my bathroom, and the fixture no longer works. Prior to my changing the switch, both the old switch and the fixture worked fine. I'm trying to figure out the root of the problem.
I tried swapping the new switch for another new switch. No change.
I tried swapping the fixture for another fixture. No change.
That suggests the issue could be a problem with the wiring between the switch and the fixture, but that seems odd to me -- what exactly would the problem be?
There's also the possibility that I'm somehow messing up the wiring of the switch somehow. This seems more likely -- human error! -- but there are only two wires here, a red and a blue. My understanding is that the red one is the hot wire and therefore the blue one is presumably the neutral, but the information I've found online about blue wiring is a little hard to decipher. See the attached image. There is also a GFCI outlet (which still works fine) in the box.
This is the light fixture box. There is no blue wire here, so I gather there is some sort of junction in between the switch and the fixture.
Finally, I discovered an old fixture box behind a (bad) patch in the drywall. I'm including an image here in case it is relevant. I note that there is a blue wire at the top of the box, and if this was the fixture used before the new one was installed, it would make sense that current is being routed through this fixture to the new one.
Here's how all three boxes in relation to one another on the wall.
I'm going to pick up a non-contact voltage tester today and try to diagnose further. Right now, I'm just planning to see whether current is actually making it 1) to the switch, 2) through the switch to the old fixture, 3) and through the switch to the new fixture.
Any other suggestions on how to figure out what is going on here? Since this was working a short time ago, I'm hoping I can fix it myself, but I will bring in an electrician if turns out to be more complicated than just installing a switch or fixture correctly.